In recent decades, the automobile industry has rapidly developed, and as the performances of an automobile develop in the direction of becoming safer, more reliable, more stable, automatic and intelligentized, and environment-friendly and energy-saving, electronic pumps gradually replace the traditional mechanical pumps and are massively used in the automotive thermal circulation systems. The electronic pumps have the advantages of having no electromagnetic interference, high efficiency and environment-friendly, and stepless speed regulation, thereby well meeting the requirements of the market.
A stator part and a rotor part of the electronic pump are completely separated by a partition, thus avoiding a liquid leakage problem of a traditional motor-type brushless direct current electronic pump. The electronic pump includes a disk-type electronic pump, an internal-rotor-type electronic pump and an external-rotor-type electronic pump. The external-rotor-type electronic pump has a good heat dissipation performance. However as discovered by the inventors that, in the external-rotor-type electronic pump, a portion, cooperating with a shaft, of the rotor part has a very small length, thus a serious vibration may be generated when the rotor part is rotating, which may adversely affect the performance and the service life of the electronic pump.